Current fertility patterns and expectations in many countries point to substantial future increases in the proportions of only children. While of undoubted social significance, demographically, will this development also be of social significance. psychologically? An answer was sought through analysis of voting records of members of the United States Congress relative to the number of their siblings: records pertaining to matters of genuine social significance and free of deficiencies characterizing data used in previous enquiries.

The analysis clearly supported the null hypothesis that no socially significant behavioral differences exist between adult singletons and nonsingletons: or, as it happens, between those with but one sibling and those with two or more. If we are to become either concerned or pleased about an increase in the proportion of singletons in the population, it will apparently have to be on some grounds other than the existence of socially significant personality differences between such persons and the rest of the population.